1. Field of the Invention
This invention relates to a method and apparatus for correcting visual aberrations resulting from ophthalmic surgery or eye injury.
2. Description of the Related Art
Visual aberrations are sometimes found as complications following ophthalmic surgery or eye injury. For instance, with respect to laser vision correction surgery, halos, glare, starbursts and night vision difficulties are often found after laser in situ keratomileusis (LASIK). As shown schematically in FIG. 1, the aberrations are caused by light scattering that is thought to be localized in the vicinity of the outer circle of the corneal flap (flap margin) produced with a microkeratome as part of the LASIK procedure.
A retrospective case-control study of LASIK patients reported visual aberrations from a sample of 841 respondents: 30% of patients experienced halos, 27% experienced glare, and 25% experienced starbursts. [Bailey M D, Mitchell G L, Dhaliwal D K, Boxer-Wachler B S, Zadnik K. Patient satisfaction and visual symptoms after laser in situ keratomileusis. Opthalmology 2003; 110:1271-1378.]
Other ophthalmic surgeries in addition to LASIK that manifest similar complications include radial keratectomy (RK), photorefractive keratectomy (PRK), and laser assisted subepithelial keratectomy (LASEK). Injury to the mid-periphery of the cornea can also cause similar visual aberrations due to scar formation or other corneal wound healing abnormalities.
When visual aberrations are present, they are disturbing at best and debilitating in the extreme. The visual disability from these aberrations is particularly noticeable in dim light and night-time circumstances. For some individuals, night driving is difficult or impossible. A description of these disabilities and post-opthalmic surgery visual aberrations can be found on the websites www.visionsimulations.com and www.surgicaleyes.org.
Previously proposed solutions to reduce glare include medication (U.S. Pat. No. 6,291,498 to Horn); optical filters (U.S. Pat. No. 6,056,397 to Berlad and U.S. Pat. No. 5,930,047 to Grunz et al.); lenses (U.S. Pat. No. 6,450,636 to Ylipelkonen, et al., U.S. Pat. No. 5,428,409 to Silverstein, and U.S. Pat. No. 5,252,997 to Christenbery); polarizing lenses (U.S. Pat. No. 6,646,801 to Sley and U.S. Pat. No. 6,424,448 to Levy); and optical apertures and shields (U.S. Pat. No. 6,386,702 to Maloncon and U.S. Pat. No. 4,828,380 to Cherian). As noted, most of the above are general glare reduction systems not focused on solving the problems of visual aberrations caused by opthalmic surgery or injury. Furthermore, the use of medicine can be considered invasive, and the optical methods can reduce the light signal. The patent to Maloncon that is specifically for use by post-operative LASIK surgery patients is a mechanical system in which the size of the viewing aperture in the device can be changed. What is needed, therefore, is a non-invasive, simple, effective method and apparatus to reduce visual aberrations resulting from surgery or injury.